A pendulum-type slide valve assembly generally includes a housing containing a pendulum valve and including an interior space and a pair of openings through which gaseous fluid can enter and exit the interior space. Pendulum valve assemblies are particularly useful in high purity gas delivery systems, such as those used in semiconductor manufacturing or other thin film coating processes. As its name implies, a pendulum valve pivots between open and closed positions, and includes a slide plate, which is usually provided as a disk or flapper, connected to a rotatably shaft by a pivot arm. In a completely opened position the slide plate is moved out of the flow path defined by the openings so that fluid can enter and exit the interior space of the housing, while in a completely closed position the slide plate is moved into sealing contact with a valve seat or annular surface surrounding one of the openings so that fluid can not enter the interior space.
The movement of the slide plate usually requires rotational (i.e., pivotal or lateral) movement between the completely opened position and an intermediate position, and then at least some longitudinal (i.e., translational, linear or axial) movement from the intermediate position to the completely closed position where the slide plate is in sealing contact with the valve seat. In order to obtain this combination of rotational and translational movement, some prior pendulum valves have typically used multiple actuator elements.
In addition, in a “standard” type gate or pendulum valve, as the gate starts to clear the opening of the valve housing, the gas flow increases rapidly. Also, since there is commonly an overlap between the gate and the opening (i.e., the gate has a larger diameter than the opening), initial movement of the gate results in little if any change in flow. Thus, the overall conductance includes very little change in flow followed by a very rapid change in flow (and vice versa as the gate is closed), which results in poor control of flow (conductance) in this operating range of the valve.
U.S. Pat. No. 6,089,537 to Olmsted, which is assigned to the assignee of the present invention and incorporated herein by reference, discloses an improved pendulum valve assembly that uses a simple rotating cam mechanism that precisely controls the rotational and longitudinal movement of the slide plate between a completely opened position and a completely closed position. The valve beneficially provides fine control near the closed position. U.S. Pat. Nos. 6,161,576, 6,328,051 and 6,409,149, which are all assigned to the assignee of the present invention and incorporated herein by reference, also disclose improved pendulum valve assemblies and systems.
U.S. Pat. No. 5,577,707 to Brida, which is assigned to VAT Holding AG, discloses a pendulum-type slide valve including a housing having a flow channel, a slide plate for controlling flow through the channel, and a seal ring surrounding the flow channel. The seal ring engages the slide plate in the closed position and disengages the slide plate in the opened position. The seal ring is removably secured to a plurality of bolts extending through bores of the housing. The housing has an annular chamber which surrounds the flow channel and into which the bores open, and the slide valve further includes an annular piston located in the annular chamber and operatively connected with the bolts. The annular piston is subjected to a force, such as a spring, and biases the seal ring against the slide plate when the latter is displaced into its closed position.
What is further desired, however, is a new and improved pendulum valve assembly including a seal ring for engaging a slide plate of the valve assembly in a closed position and disengaging the slide plate in an opened position. Preferably, the seal ring will be easily and quickly removable for maintenance and cleaning of the valve assembly.